scholarly journals Coupling of dual mass-transferring white dwarf binaries as a variable gravitational-wave emitter

2020 ◽  
Vol 496 (4) ◽  
pp. 5575-5583
Author(s):  
Naoki Seto
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
White Dwarf ◽  
Simplified Model ◽  
Model Parameters ◽  
Body System ◽  
Amplitude Variation ◽  
Synchronous State ◽  
Orbital Periods ◽  
Small Period

ABSTRACT We study evolution of a hierarchical four-body (2 + 2) system composed by a pair of mass-transferring white dwarf binaries. Applying a simplified model around the synchronous state of two inner orbital periods, we newly find that the four-body system could settle down to a limit cycle with a small period gap. The period gap generates an amplitude variation of emitted gravitational waves as a beat effect. Depending on model parameters, the beat period could be 1–10 yr and a large amplitude variation might be observed by space gravitational-wave detectors.

scholarly journals White dwarf binaries and the gravitational wave foreground

2014 ◽  
Vol 10 (S312) ◽  
pp. 289-295
Author(s):  
Matthew Benacquista
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Frequency Band ◽  
White Dwarf ◽  
Initial Orientation ◽  
Careful Choice ◽  
Instrument Noise

AbstractGalactic white dwarf binaries will be an abundant source of gravitational waves in the mHz frequency band of space-based detectors such as eLISA. A few thousand to a few tens of thousands of these systems will be individually resolvable by eLISA, depending on the final detector configuration. The remaining tens of millions of close white dwarf binaries will create an unresolvable anisotropic foreground of gravitational waves that will be comparable to the instrument noise of eLISA at frequencies below about a mHz. Both the resolvable binaries and the foreground can be used to better understand this population. Careful choice of the initial orientation of eLISA can mitigate this foreground in searches for other sources.

scholarly journals Predicting the LISA white dwarf binary population in the Milky Way with cosmological simulations

2019 ◽  
Vol 490 (4) ◽  
pp. 5888-5903 ◽  
Author(s):  
Astrid Lamberts ◽  
Sarah Blunt ◽  
Tyson B Littenberg ◽  
Shea Garrison-Kimmel ◽  
Thomas Kupfer ◽  
...  
Keyword(s):  
Gravitational Wave ◽  
White Dwarf ◽  
Milky Way ◽  
Thick Disc ◽  
Distance Distributions ◽  
The Galaxy ◽  
Stellar Halo ◽  
Galaxy Model ◽  
Orbital Periods ◽  
Binary Evolution

ABSTRACT White dwarf binaries with orbital periods below 1 h will be the most numerous sources for the space-based gravitational wave detector Laser Interferometer Space Antenna (LISA). Based on thousands of individually resolved systems, we will be able to constrain binary evolution and provide a new map of the Milky Way and its close surroundings. In this paper we predict the main properties of populations of different types of detached white dwarf binaries detected by LISA over time. For the first time, we combine a high-resolution cosmological simulation of a Milky Way-mass galaxy (taken from the FIRE project) with a binary population synthesis model for low- and intermediate-mass stars. Our Galaxy model therefore provides a cosmologically realistic star formation and metallicity history for the Galaxy and naturally produces its different components such as the thin and thick disc, the bulge, the stellar halo, and satellite galaxies and streams. Thanks to the simulation, we show how different Galactic components contribute differently to the gravitational wave signal, mostly due to their typical age and distance distributions. We find that the dominant LISA sources will be He–He double white dwarfs (DWDs) and He–CO DWDs with important contributions from the thick disc and bulge. The resulting sky map of the sources is different from previous models, with important consequences for the searches for electromagnetic counterparts and data analysis. We also emphasize that much of the science-enabling information regarding white dwarf binaries, such as the chirp mass and the sky localization, becomes increasingly rich with long observations, including an extended mission up to 8 yr.

scholarly journals ZTF J1901+5309: a 40.6-min orbital period eclipsing double white dwarf system

2020 ◽  
Vol 494 (1) ◽  
pp. L91-L96 ◽  
Author(s):  
Michael W Coughlin ◽  
Kevin Burdge ◽  
E Sterl Phinney ◽  
Jan van Roestel ◽  
Eric C Bellm ◽  
...  
Keyword(s):  
Gravitational Wave ◽  
Orbital Period ◽  
White Dwarf ◽  
Binary Systems ◽  
Demographic Analysis ◽  
Effective Temperatures ◽  
Orbital Periods ◽  
High Cadence

ABSTRACT The Zwicky Transient Facility has begun to discover binary systems with orbital periods that are less than 1 h. Combined with dedicated follow-up systems, which allow for high-cadence photometry of these sources, systematic confirmation and characterization of these sources are now possible. Here, we report the discovery of ZTF J190125.42+530929.5, a 40.6-min orbital period, eclipsing double white dwarf binary. Both photometric modelling and spectroscopic modelling confirm its nature, yielding an estimated inclination of $i = 86.2^{+0.6}_{-0.2}\, \rm deg$ and primary and secondary effective temperatures of $\textrm{{T}}_\textrm{eff} = 28\,000^{+500}_{-500}$ and $17\,600^{+400}_{-400}\, \mathrm{ K}$, respectively. This system adds to a growing list of sources for future gravitational-wave detectors and contributes to the demographic analysis of double degenerates.

scholarly journals Gravitational waves from dynamical tides in white dwarf binaries

2019 ◽  
Author(s):  
L O McNeill ◽  
R A Mardling ◽  
B Müller
Keyword(s):  
Angular Momentum ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Frequency Band ◽  
White Dwarf ◽  
White Dwarfs ◽  
Momentum Exchange ◽  
Tidal Dissipation ◽  
Tidal Forcing ◽  
Tidal Torques

Abstract We study the effect of tidal forcing on gravitational wave signals from tidally relaxed white dwarf pairs in the LISA, DECIGO and BBO frequency band (0.1 − 100 mHz). We show that for stars not in hydrostatic equilibrium (in their own rotating frames), tidal forcing will result in energy and angular momentum exchange between the orbit and the stars, thereby deforming the orbit and producing gravitational wave power in harmonics not excited in perfectly circular synchronous binaries. This effect is not present in the usual orbit-averaged treatment of the equilibrium tide, and is analogous to transit timing variations in multiplanet systems. It should be present for all LISA white dwarf pairs since gravitational waves carry away angular momentum faster than tidal torques can act to synchronize the spins, and when mass transfer occurs as it does for at least eight LISA verification binaries. With the strain amplitudes of the excited harmonics depending directly on the density profiles of the stars, gravitational wave astronomy offers the possibility of studying the internal structure of white dwarfs, complimenting information obtained from asteroseismology of pulsating white dwarfs. Since the vast majority of white-dwarf pairs in this frequency band are expected to be in the quasi-circular state, we focus here on these binaries, providing general analytic expressions for the dependence of the induced eccentricity and strain amplitudes on the stellar apsidal motion constants and their radius and mass ratios. Tidal dissipation and gravitation wave damping will affect the results presented here and will be considered elsewhere.

scholarly journals Cosmology with the Einstein Telescope: No Slip Gravity model and redshift specifications

2021 ◽  
Author(s):  
Ayan Mitra ◽  
Jurgen Mifsud ◽  
David F Mota ◽  
David Parkinson
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Gravity Model ◽  
Modified Gravity ◽  
Cosmological Parameters ◽  
Gravitational Theory ◽  
Model Parameters ◽  
Einstein Telescope ◽  
Interferometric Detectors ◽  
Parameter Constraints

Abstract The Einstein Telescope and other third generation interferometric detectors of gravitational waves are projected to be operational post 2030. The cosmological signatures of gravitational waves would undoubtedly shed light on any departure from the current gravitational framework. We here confront a specific modified gravity model, the No Slip Gravity model, with forecast observations of gravitational waves. We compare the predicted constraints on the dark energy equation of state parameters $w_0^{}-w_a^{}$, between the modified gravity model and that of Einstein gravity. We show that the No Slip Gravity model mimics closely the constraints from the standard gravitational theory, and that the cosmological constraints are very similar. The use of spectroscopic redshifts, especially in the low–redshift regime, lead to significant improvements in the inferred parameter constraints. We test how well such a prospective gravitational wave dataset would function at testing such models, and find that there are significant degeneracies between the modified gravity model parameters, and the cosmological parameters that determine the distance, due to the gravitational wave dimming effect of the modified theory.

scholarly journals Mapping the gravitational-wave sky with LISA: A bayesian spherical harmonic approach

2021 ◽  
Author(s):  
Sharan Banagiri ◽  
Alexander Criswell ◽  
Tommy Kuan ◽  
Vuk Mandic ◽  
Joseph D Romano ◽  
...  
Keyword(s):  
Angular Distribution ◽  
Gravitational Wave ◽  
White Dwarf ◽  
Spherical Harmonic ◽  
Simplified Model ◽  
Wave Power ◽  
Frequency Content ◽  
Mass Ratio ◽  
Angular Structure ◽  
Bayesian Algorithm

Abstract The millihertz gravitational-wave frequency band is expected to contain a rich symphony of signals with sources ranging from galactic white dwarf binaries to extreme mass ratio inspirals. Many of these gravitational-wave signals will not be individually resolvable. Instead, they will incoherently add to produce stochastic gravitational-wave confusion noise whose frequency content will be governed by the dynamics of the sources. The angular structure of the power of the confusion noise will be modulated by the distribution of the sources across the sky. Measurement of this structure can yield important information about the distribution of sources on galactic and extra-galactic scales, their astrophysics and their evolution over cosmic timescales. Moreover, since the confusion noise is part of the noise budget of LISA, mapping it will also be essential for studying resolvable signals. In this paper, we present a Bayesian algorithm to probe the angular distribution of the stochastic gravitational-wave confusion noise with LISA using a spherical harmonic basis. We develop a technique based on Clebsch-Gordan coefficients to mathematically constrain the spherical harmonics to yield a non-negative distribution, making them optimal for expanding the gravitational-wave power and amenable to Bayesian inference. We demonstrate these techniques using a series of simulations and analyses, including recovery of simulated distributed and localized sources of gravitational-wave power. We also apply this method to map the gravitational-wave foreground from galactic white-dwarfs using a simplified model of the galactic white dwarf distribution.

scholarly journals Gravitational waves from mountains in newly born millisecond magnetars

2021 ◽  
Vol 502 (4) ◽  
pp. 4680-4688
Author(s):  
Ankan Sur ◽  
Brynmor Haskell
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Massive Star ◽  
Gamma Ray ◽  
Dipole Radiation ◽  
X Ray ◽  
Binary Neutron Star ◽  
Spin Period ◽  
Lower Maximum ◽  
Wave Emission

ABSTRACT In this paper, we study the spin-evolution and gravitational-wave luminosity of a newly born millisecond magnetar, formed either after the collapse of a massive star or after the merger of two neutron stars. In both cases, we consider the effect of fallback accretion; and consider the evolution of the system due to the different torques acting on the star, namely the spin-up torque due to accretion and spin-down torques due to magnetic dipole radiation, neutrino emission, and gravitational-wave emission linked to the formation of a ‘mountain’ on the accretion poles. Initially, the spin period is mostly affected by the dipole radiation, but at later times, accretion spin the star up rapidly. We find that a magnetar formed after the collapse of a massive star can accrete up to 1 M⊙, and survive on the order of 50 s before collapsing to a black hole. The gravitational-wave strain, for an object located at 1 Mpc, is hc ∼ 10−23 at kHz frequencies, making this a potential target for next-generation ground-based detectors. A magnetar formed after a binary neutron star merger, on the other hand, accretes at the most 0.2 M⊙ and emits gravitational waves with a lower maximum strain of the order of hc ∼ 10−24, but also survives for much longer times, and may possibly be associated with the X-ray plateau observed in the light curve of a number of short gamma-ray burst.

scholarly journals The White Dwarf Mass and Orbital Period Distribution in Zero-Age Cataclysmic Binaries

1989 ◽  
Vol 114 ◽  
pp. 440-442
Author(s):  
M. Politano ◽  
R. F. Webbink
Keyword(s):  
Star Formation ◽  
White Dwarf ◽  
Galactic Disk ◽  
Orbital Energy ◽  
Orbital Parameter ◽  
Orbital Parameters ◽  
Cataclysmic Binaries ◽  
Magnetic Braking ◽  
Orbital Periods ◽  
The Individual

A zero-age cataclysmic binary (ZACB) we define as a binary system at the onset of interaction as a cataclysmic variable. We present here the results of calculations of the distributions of white dwarf masses and of orbital periods in ZACBs, due to binaries present in a stellar population which has undergone continuous, constant star formation for 1010 years.Distributions of ZACBs were calculated for binaries formed t years ago, for log t = 7.4 (the youngest age at which viable ZACBs can form) to log t = 10.0 (the assumed age of the Galactic disk), in intervals of log t = 0.1. These distributions were then integrated over time to obtain the ZACB distribution for a constant rate of star formation. To compute the individual distributions for a given t, we require the density of systems forming (number of pre-cataclysmics forming per unit volume of orbital parameter space), n£(t), and the rates at which the radii of the secondary and of its Roche lobe are changing in time, s (t) and L, s (t), respectively. In calculating nf(t), we assume that the distribution of the orbital parameters in primordial (ZAMS) binaries may be written as the product of the distribution of masses of ZAMS stars (Miller and Scalo 1979), the distribution of mass ratios in ZAMS binaries (cf. Popova, et al., 1982), and the distribution of orbital periods in ZAMS binaries (Abt 1983). In transforming the the orbital parameters from progenitor (ZAMS) to offspring (ZACB) binaries, we assume that all of the orbital energy deposited into the envelope during the common envelope phase leading to ZACB formation goes into unbinding that envelope. R.L, s (t) is determined from orbital angular momentum loss rates due to gravitational radiation (Landau and Lifshitz 1951) and magnetic braking (γ = 2 in Rappaport, Verbunt, and Joss 1983). We turn off magnetic braking if the secondary is completely convective.

scholarly journals Gravitational wave–gauge field dynamics

2017 ◽  
Vol 26 (12) ◽  
pp. 1742005 ◽  
Author(s):  
R. R. Caldwell ◽  
C. Devulder ◽  
N. A. Maksimova
Keyword(s):  
Quantum Gravity ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Gauge Field ◽  
Linear Combination ◽  
Effective Mass ◽  
Normal Modes ◽  
New Approaches ◽  
Insight Into

The dynamics of a gravitational wave propagating through a cosmic gauge field are dramatically different than in vacuum. We show that a gravitational wave acquires an effective mass, is birefringent, and its normal modes are a linear combination of gravitational waves and gauge field excitations, leading to the phenomenon of gravitational wave–gauge field oscillations. These surprising results provide an insight into gravitational phenomena and may suggest new approaches to a theory of quantum gravity.

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